By ERIC TUCKER, BRETT ZONGKER and LOLITA C. BALDORAssociated Press
WASHINGTON (AP) - The deadly attack at the Washington Navy Yard was carried out by one of the military's own: a defense contract employee and former Navy reservist who used a valid pass to get onto the installation and started firing inside a building, killing 12 people before he was slain in a gun battle with police.
The shooting was the deadliest on a military installation in the U.S. since the tragedy at Fort Hood, Texas, in 2009.
Law enforcement officials say gunman Aaron Alexis carried three weapons at the Navy Yard: an AR-15 assault rifle, a shotgun and a handgun he took from an officer at the scene.
Investigators say his motive is a mystery.
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